The TEK4 monoclonal antibody reacts with mouse Tie-2, also known as CD202. A member of the tyrosine kinase receptor family, Tie-2 is expressed on endothelial and a subset of hematopoietic cells and is believed to play a role in both angiogenesis and hematopoiesis during development of the mouse embryo. In fetal liver and adult bone marrow, Tie-2 is expressed by a subpopulation of hematopoietic progenitor cells characterized as Lineage markers-, c-Kit+, Sca1+ cells. Long-term multilineage repopulating cells were detected in Tie-2+, Lineage-, c-Kit+, Sca1+ cells but not in Tie-2-, Lineage-, c-Kit+, Sca1+ cells.